FIELD OF THE INVENTION
The invention is directed to an electrical capacitor composed of a consolidated winding, or an individual consolidated stack, the winding or stack being formed of plastic plies layered to one another and provided with regenerably thin coatings of valve metal.
In particular the coatings alternately extend up to the ends of two projections from ply to ply, these projections being formed by an incision which proceeds in the direction of the thickness of the winding or of the stack, and proceeds roughly in the middle of a side thereof. PA1 The surfaces formed by the ends of the projections in the consolidated winding, or stack, are provided with metal layers to provide electrical contacting and being manufactured by metaI spraying, these metal layers connecting the coatings to one another and serving for the fastening of external power leads. PA1 The coatings cover the surfaces of the plastic plies practically up to the edges at the longitudinal sides as well as up to the two ends of the projections and, as warranted, up to the edge of the upper narrow side of the stack which lies opposite the narrow side containing the incision; PA1 The projections are alternately provided with metal-free insulating strips and residual metal strips from plastic ply to plastic ply. PA1 The depth of the incision is either greater than the width of the residual metaI strips or, preferably, coincides with the inner edges of the insulating strips or extends beyond these edges into the winding or into the stack in the direction of its longitudinal axis. PA1 (a) The two metallized bands are provided with intermittent, metal-free insulating strips before or during winding. Laser beams generate the metal-free strips in the regions of the edges of the metallized bands and spaced at intervals in a winding direction such that the insulating strips lie in a plane perpendicular to the winding axis when wound onto the drum. Both the ends as well as the beginnings of the insulating strips extend into the region of the subsequent incision or go slightly beyond this region. PA1 (b) When being wound onto the drum, the bands are guided such that the centers of the insulating strips of the upper band are arranged symmetrically above the centers of the interstices between the insulating strips of the lower band in the finished mother capacitors. PA1 (c) After the winding and consolidation of the initial capacitor or, respectively, the mother capacitors, and while still on the drum, at least those end faces formed by the edges are provided with a metal layer by metal spraying. PA1 (d) Before or after dividing the initial capacitor into individual mother capacitors, incisions are made perpendicular to the winding direction in the middle between two respective cut lines from both sides of the mother capacitor. The two projections of each capacitor arise due to the width and depth of these incisions. PA1 (e) The mother capacitors are separated into the individual capacitors -- potentially after fastening power leads thereto -- by making insulating saw cuts both along cut lines which proceed through the centers of the insulating strips, as well as along a cut line which lies parallel to the edges in the middle of the mother capacitor. PA1 (f) Finally, the individual capacitors are finished by applying cap-shaped or other power leads, insofar as these were not already attached in method step e). PA1 (a) Regenerably thin metal layers are present as coatings on both surfaces of each and every plastic ply. PA1 (b) Furthermore, an extremely thin plastic layer is provided as a dielectric on one or on both coatings of every plastic ply, or on both coatings of every second plastic ply. The extremely thin plastic layer generally completely covers the coating, extends into the region of the residual metal strips, and is at least partially removed above the insulating strips.
The invention is also directed to a method for the manufacture of such a capacitor wherein two regenerably thin, metallized bands on plastic plies, particularly comprising a corrugated cut along one edge, are layered on a drum to form an initial capacitor. The initial capacitor is divided into the desired individual capacitors perpendicular to the layer planes. For a plurality of plastic plies and coatings forming a potential mother capacitor, non-active cover plies are provided, parting plies are arranged thereon and cover plies are in turn arranged thereon and the plastic plies that have the coatings are in turn arranged thereon for the next mother capacitor. The initial capacitor which has been formed in this fashion is provided with end contact layers and is subsequently divided in the region of the intermediate parting plies and in a direction perpendicular thereto. In particular, the method steps are as follows:
Capacitors which have all of these initially cited features, and methods which have the recited method steps are extensively described with respect to stack capacitors and with a broad discussion of prior art in German published application No. 3342 329, which corresponds to the European published application EP-A No. 3-0 144 857 and to U.S. Pat. 4,563,724. Corresponding wound capacitors and methods for the manufacture thereof are disclosed in German published application No. 35 17 435, and in European-A No. 3 0 201 771 and U.S. Pat. No. 4,639,832 which correspond thereto.
A variety of terms known in the art are included among those employed in describing the present invention. These terms are explained in detail in U.S. Pat. No. 4,563,724 at the respectively cited passages. Amoung these terms are: "insulating saw cut" (cf. U.S. Patent, column 3, lines 18-28 and column 7, lines 3-11 and lines 60-65), "corrugated cut" or "wavy cut" (cf. column 3, lines 50-62 and column 8, lines 55-65), "cover layers" (cf. column 7, lines 42-47), "regeneratability" (cf. column 2, lines 38-46), "Schoopage method" (cf. column 9, lines 13-19 and column 10, lines 49-52), as well as "synchronized control of the laser beam pulses" (cf. column 11, lines 27-33).
A known capacitor of the species recited and a known method for the manufacture thereof exhibit a number of major advantages which are described in U.S. Pat. No. 4,563,724 in column 4, lines 47-53; column 7, lines 12-21; and column 10, lines 24-35 and lines 63-68. More specifically, the advantages are essentially that a largely low-induction capacitor is achieved which is suitable for a grid dimension of 2.5 mm in whose manufacture the width of the bands to be wound is not subject to any manufacturing limitation and which can be manufactured in extremely high piece numbers in an especially efficient way.
Despite all of these advantages, it can be necessary to further increase the volume capacitance of such a capacitor in order to accommodate extremely high capacitances in optimally small volumes. This requirement is met in the known wound, or stacked, capacitors by applying extremely thin dielectric layers, for example in the form of lacquer layers or of plastic layers produced by glow polymerization of monomers from the vapor phase. However, the prior art known in this context provides no teaching as to how an initially recited, low-induction capacitor must be constructed in order to achieve a high volume capacitance by the use of extremely thin dielectric layers.
The prior art which is relevant in this context, thus, obviates neither the structural format nor the manufacturing method of such an improved capacitor. For example, U.S. Pat. No. 3,252,830 discloses an electrical capacitor and a method for the manufacture thereof wherein a metal layer is first applied to a carrier foil, this metal layer leaving a metal-free strip free in the region of an edge. By glow polymerization of various plastic materials recited therein, a dielectric layer is generated on this first metal layer, this dielectric layer completely covering the first metal layer and the metal-free edge strips. A second metal layer is then applied thereto, leaving a metal-free strip free at the opposite edge. The carrier band prepared in this way is wound to form a normal wound-capacitor and is contacted at the end face in the way standard for these cases. This electrical wound capacitor includes two power lead wires proceeding in an axial direction.
The U.S. Pat. No. 3,252,830 (cf. column 6, lines 7-15) also contains the teaching that various other forms are possible as wound, flat or muIti-layer structures, whereby, as an example, flat multi-layer capacitors could be employed for a low-voltage capacitor having a high capacitance. A parallel circuit is formed in such capacitor, whereas a corresponding series circuit is recommended for high-voltage capacitors. Even given knowledge of the aforementioned U.S. Pat. No. 4,563,724, a person skilled in the art is not lent a teaching toward low-inductive capacitors of the species initially cited and the manufacturing method comprising all the recited advantages.
The situation is the same in the case of U.S. Pat. No. 3,069,283, which discloses a more efficient method for the manufacture of wound capacitors. Namely, it is not a single carrier band that is pre-treated but, rather, a carrier band whose widths amounts to a multiple of the width required for the later wound capacitor. In this rationalized manufacturing method, strips proceeding in a band direction which leave intermediate surfaces free are first applied to the carrier foil upon employment of masks. Taking certain, mutual dislocations into consideration, extremely thin plastic films are then applied to these strips by glow polymerization, the plastic films being likewise applied in strip form. Finally, metal for the cooperating electrodes is applied in strip form, likewise taking certain dislocations into consideration. The band prepared in this way is then divided into individual bands in the band direction, and individual wound capacitors are then manufactured therefrom.
The Japanese periodical "National Technical Report", Vol. 26, No. 2, April 1980, pages 231-236 describes a capacitor having the designation "TF-capacitor ECQ-V" whose manufacturing method and whose structure are explained in conjunction with the enclosed FIGS. 2, 3 and 4. This capacitor is a normal stacked capacitor which -- with the exception of the additionally provided, extremely thin lacquer layers -- was admitted as prior art in the specification of U.S. Pat. No. 4,563,724 (cf col. 7, lines 39-65 and FIG. 5 therein).
In contrast to the disclosed capacitors having extremely thin plastic layers of glow polymer, the known "TF-capacitors" contain layers of lacquer, particularly of polycarbonate lacquer, as extremely thin layers and place the carrier members in the field space because metal-free insulating strips are present at opposite edges of the carrier. Due to the considerably thicker carrier layers in comparison to the lacquer layers or given employment of carrier layers that are likewise thin, however, the reducing influence on the volume capacitance is not very great and is accepted. Neither viewed by itself nor in combination with other prior art, thus, does the Japanese periodical provide a teaching of low-induction capacitors with an increased volume capacitance.
German AS No. 22 27 751, which corresponds to U.S. Pat. No. 3,855,507, discloses an electrical wound or stacked capacitor and methods for the manufacture thereof. This capacitor is regenerable, having carrier foils metallized on both sides in the field-free space and contains intermediate layers under the metal coatings. Extremely thin dielectric layers of plastic manufactured by lacquering are provided above the metal coatings, these dielectric layers of plastic cover the metal coatings up to the edge and potentially extending up to the end faces. Metal drops are applied to an end face contact layer, which penetrate the extremely thin dielectric layers without further ado as a result of their kinetic energy and their temperature. Nonetheless, these capacitors must have edge regions alternating at opposite face ends which are free of the metal of the coatings, so that this publication likewise provides no teaching as to how one should proceed in order to obtain low-induction capacitors of the species under consideration here.